The boulder is a crystalline rock consisting of pyroxene (chrome-diopside), garnet, and a little olivine, and is studded with diamond crystals; a portion of it is preserved in the British Museum (Natural History).
They are soft and lustrous, with a peculiarly smooth feel, and though often confounded with mica-schists may be distinguished by their richness in magnesia; many of them contain tremolite or actinolite; others have residual grains of olivine or augite; and here also every gradation can be found between the unmodified igneous types and the perfectly metamorphic schists.
They found relatively large grains and many small crystals of a mineral called olivine.
The most common ferromagnesian minerals include olivine, pyroxene, amphibole and mica.
The Green Sand Beach in the south of the island of Hawaii (Big Island) contains just this green, well-rounded olivine.
